Why we chose it: TripAdvisor selected this Central American speck of land as the best island in the world for the second year in a row. You'll find great snorkeling (and, if you're with fishermen, possibly dinner) and the oft-employed cliche--gin-clear Caribbean waters--will resonate after you've seen them, although there's nothing cliched about them. Settle down with a Belikin beer at sunset and you'll know life is good.
Potential drawbacks: It's an islet so your journey isn't over when you land at the airport in Belize City. You can take a ferry or a small plane. If you're prone to seasickness or you hate the idea of a small plane, you'd best choose another location.